Could it be that 'deliciae' is simply the nominative, with 'meae puellae' being the dative of possesive, or genitive? There's really no change in the translation if "meae puellae" is taken to be either: "Sparrow, the delight to my girl" or "Sparrow, my girl's delight."

The word deliciae is in the genitive case (singular). The word puellae is also in the genitive case (singular).

These words mean âsparrow of my delicious girlâ and nothing else.

I see that it is difficult to Englishmen to understand Latin texts, because you are not accustomed to cases. I think that it might be advisable to study the Russian language if you really want to understand Latin texts. The use of the genitive, dative and other cases in the Russian language is similar to that in the Latin language. The Russian poetry resembles the Latin poetry in some respects. Yet it is easier to learn a modern language.

The logic of the Latin language is similar to that of the Russian language in many respects.

I think you are mistaken Olga. Deliciae does not agree with puellae, although technically it could. If you have Garrison's text he notes that Catullus uses the world deliciae in the plural 5 times with the meaning of pet or darling. Grammatically it is in apposition of passer, making it nominative plural with a singular meaning.

Also in your rearranging of the word order you have placed a comma after nescio, separating it from quid. The phrase (sometimes written as one word) "nescio quid" is an idiom that can just be translated as "something."

In every text I have read of Carmen 2, the editor places a comma after passer, indicating that deliciae is in apposition to passer. This line could be slightly ambiguous, but I think it is apparent to experienced Latinists that it is best translated "Sparrow, the delights of my girl."